A couple main reasons. 1) 64 vs 32. I can't keep all my Final Fantasy games on my Edge without running into storage issues. Sick of shuffling things around. I will not buy a phone under 64 GB from this point forward. 2) S Pen. Had a Galaxy Note 8 years ago and loved the pen. Wanting to get back to that. 3) Slightly larger screen with edge, but less edge. I love the S7 Edge, but the larger screen with slightly less curved edges is better. 3) I'm a gadget *****. Not gonna lie, I have an addition to buying tech I find cool.
There is one thing that is actually a detractor for me and that's USB-C. I'm glad that it's the future, but the messiness of bad cables, different charging standards, unclear interoperation with previous USB, and a plethora of non-USB-C cables and adapters lying around all made me question getting it. In the end, I decided I can handle it. LOL